The present disclosure relates to damping sound and vibration in large hollow golf club heads by providing a damper between the sole and top wall or crown of such golf clubs.
Currently, large, hollow metal driver-type golf club heads typically generate a strong and often objectionable, sharp ringing sound immediately after impact of a face of the club head on a ball. When hollow metal heads first became available, they were often filled with a vibration-damping foam material. This added unwanted weight. What was worse, because of its lack of rigidity, the added weight of the foam did not participate fully in the impact. This caused reduced driving distance. More recently with even larger heads of this type, the ringing sound was allowed by club head designers, even with the objection of some golfers.
Test have shown that the impact of a ball on the club face of a typical modern hollow golf club head produces an amplitude of vibration of the crown (top wall) and sole (bottom wall) of the head such that the crown-sole distance expands about 0.02 inch during and immediately following impact. This causes a predominately crown-sole oscillation that persists for the order of one second and emits a sharp sound in the range of about 1000 to 5000 thousand cycles per second. This is in the general frequency range of maximum audible sensation to the ears of typical humans. The stiffness for a force tending to reduce the crown-sole distance was found to be about 2000 pounds of force per inch of deformation. Because peak forces on the club face at impact are in the range of 2500 pounds, the club head must be designed to have far greater stiffness for face-rear vibrations than the 2000 pounds per inch of crown-sole stiffness. For this reason, oscillations in the face-rear direction are far smaller, higher frequency, and emit much less audible sound.
Thus, reducing vibrations in the crown-sole direction is important for overall sound reduction. Vibrations in the face-rear direction are relatively unimportant. The damping structure should add fewer than about 2 grams of mass, because such mass may not significantly participate in the impact.